Problem with Central Heating?

We have a Vaillant ecoMax Combi boiler and a Drayton control SM1 switch. We have hot water but no central heating When the switch it turned to on 24hrs the red light comes on however there is no sound to indicate the central heating is on and the thermostat light is off too. I have turned the thermostat right up... show more We have a Vaillant ecoMax Combi boiler and a Drayton control SM1 switch.
We have hot water but no central heating
When the switch it turned to on 24hrs the red light comes on however there is no sound to indicate the central heating is on and the thermostat light is off too. I have turned the thermostat right up but no success also tried tweaking the pump inside the boiler but nothing. I noticed earlier there was a code S.30 which is 'No heating demand from external controls'
Any help appreciated
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